fix(python): make job schedulers advance and support the postgres backend

[manast]

Job schedulers were effectively broken in the Python package: the worker
never advanced a scheduler to its next iteration, so upsertJobScheduler
only ever materialized the first job and the schedule stopped. They were
also unavailable on the PostgreSQL backend.

• Advance the scheduler in Worker.nextJobFromJobData (mirrors the Node
  worker): when a processed job carries a repeatJobKey, upsert its
  scheduler for the next iteration.
• Route all scheduler datastore operations through the Backend
  abstraction (addJobScheduler, updateJobSchedulerNextMillis,
  removeJobScheduler, isJobScheduler, getJobScheduler, getJobSchedulers,
  getJobSchedulersCount) and implement them in both the Redis and
  PostgreSQL adapters, so JobScheduler is backend-agnostic.
• Drop the Redis-only NotImplementedError gate in Queue/Worker.jobScheduler.

fixes #4483

[Copilot]

Pull request overview

Fixes Python job scheduler advancement (repeatable job factories) and makes schedulers backend-agnostic so they work on both Redis and PostgreSQL, addressing #4483.

Changes:

• Advance job schedulers when workers pick up scheduler-produced jobs (Worker.nextJobFromJobData), ensuring iterations continue beyond the first.
• Route scheduler datastore operations through the Backend abstraction and implement them in both Redis and Postgres backends.
• Add regression tests for worker advancement and lazy jobScheduler initialization; adjust CI postgres job to skip when Node/Lua are unchanged.

Reviewed changes

Copilot reviewed 8 out of 8 changed files in this pull request and generated 1 comment.

Show a summary per file

File	Description
python/tests/job_scheduler_test.py	Adds regression tests for worker-driven scheduler advancement and lazy jobScheduler creation.
python/bullmq/worker.py	Adds lazy jobScheduler on Worker and advances schedulers when consuming scheduled jobs.
python/bullmq/queue.py	Removes Redis-only guard so schedulers can be used with non-Redis backends.
python/bullmq/job_scheduler.py	Makes JobScheduler backend-agnostic by calling backend scheduler APIs instead of Redis scripts/client.
python/bullmq/backends/redis_backend.py	Implements scheduler operations on the Redis backend via Lua scripts + Redis data structures.
python/bullmq/backends/postgres_backend.py	Implements scheduler operations on the Postgres backend via SQL commands and row mapping.
python/bullmq/backend.py	Extends the backend interface with scheduler-related abstract methods.
.github/workflows/test.yml	Skips node/postgres test steps when Node/Lua inputs are unchanged.

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🎉 This PR is included in version 6.0.8 🎉

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[github-actions]

🎉 This PR is included in version 3.0.4 🎉

The release is available on:

• vpy3.0.4
• GitHub release

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